program main
    implicit none
    integer(8)::N,i,ans=0,flg,is
    read*,N
    do i=12,N,3
        if(i<=100)then
            ans=ans+1
        else
            flg=1
            is=i
            do while (is>0)
                if(mod(mod(is,10),3)/=0)flg=0
                is=is/10
            end do
            if(flg==1)ans=ans+1
        end if
    end do

    print'(i0)',ans
end program main